The objective of the proposed research is to define the effects of delta 9-tetrahydrocannabinol and cannabidiol on electrophysiological properties of the nervous system, particularly as these effects relate to the mechanism or mechanisms of the anticonvulsant action of the cannabinoids. These studies will include two different preparations of conscious rats with chronically implanted electrodes: One preparation will have a focal epilepsy induced by cortical implantation of cobalt; in the other, epileptic-like activity will be evoked by focal electrical stimulation of the hippocampus. Furthermore, the research will include a traditional electrophysiological model for the study of synaptic transmission, the monosynaptic pathway in the unanesthetized spinal cat. The model systems will be used to measure the influence of the cannabinoids on focal epileptic activity, on seizure spread within the CNS and on posttetanic potentiation. The results of these studies will provide a basis for the development of hypotheses for the mechanism of the anticovulsant action of the cannabinoids.